CN111051682B

CN111051682B - Device for detecting the condition of an injector

Info

Publication number: CN111051682B
Application number: CN201880048736.2A
Authority: CN
Inventors: 诺伯特·舒班克; 理查德·皮尔克; 洛兰·杜文努
Original assignee: Liebherr Components Deggendorf GmbH
Current assignee: Liebherr Components Deggendorf GmbH
Priority date: 2017-07-20
Filing date: 2018-07-20
Publication date: 2022-08-02
Anticipated expiration: 2038-07-20
Also published as: CN111051682A; US20200256297A1; DE102017116379A1; ES2939061T3; EP3642473A1; WO2019016380A1; EP3642473B1; US11111892B2

Abstract

An apparatus for condition detection of an injector comprising: an injector for injecting fuel into a combustion chamber of an engine; a switch configured to change a switch state of the injector according to a state of the injector; and an evaluation unit for detecting a switching state of the switch, wherein a first switching contact of the switch is connected to the electrical input line of the injector and a second switching contact of the switch is connected to ground, the evaluation unit being configured with a first current measurer for the current flowing into the injector and the switch and a second current measurer for the current flowing into the injector.

Description

Device for detecting the condition of an injector

Technical Field

The present invention relates to a device for detecting the state of an injector or an injector having a corresponding state detection device, and to a method for determining the state of an injector.

Background

Fuel injectors or injectors are commonly used to inject fuel into the combustion chambers of an engine. In this case, it is advantageous for an engine in which such an injector is present, also in terms of the overall product life of the injector, if the control unit is informed of the exact opening timing of the injector, so that for example a particularly narrow error band exists for the injection quantity of fuel discharged by the injector.

In addition, it is advantageous for a number of control or monitoring functions of the engine if the exact injection time for the injector to release fuel is known.

It is known from the prior art to use an electrical switch for the state detection of the injector. In this case, the switch is closed when the injector is not energized and the needle of the injector is not moving or it is ensured that no fuel escapes from the injector. As soon as the valve needle is removed from its valve seat, the electric switch changes its state, i.e. into the open or closed state. When the valve needle moves back towards the valve seat, the switch again changes its state.

In the simplest form of condition detection of the injector, a total of four wires are connected in the housing of the injector, in which a switch is also arranged. Two wires are provided for the injector itself and the other two wires are assigned to the switch. However, this has the disadvantage that a unit designed in this way requires a large number of cables.

If a 3-or 4-stage plug is used, i.e. 3 or 4 wires are connected to the injector by means of a switch, no additional work is required by the detection circuit. On the other hand, this situation means additional work to be performed on the injector due to the multiple components and the large size of the connecting parts.

In a variant of this type (also known from the prior art), the switching contact (schalterkontkotate) is arranged not directly in contact with the housing of the injector or is arranged in an insulated manner in the housing of the injector. Such a representative scheme is shown in fig. 1. Here, one pole of the switch is connected via a resistor to a pin of the injector or to a pin of a solenoid valve which actuates the injector. The other pole of the switch is also connected to the housing of the injector. In this case, the injector itself is typically connected to ground, which may be the engine block, for example, when used on a vehicle. In this embodiment, only two cables or wires exit the housing.

In normal operation, the injector or a solenoid valve operating the injector is energized, thereby triggering a mechanical and/or hydraulic movement of the valve needle. Movement of the valve needle again opens or closes the switch. For example, it can be provided that the switch is closed by removing the voltage.

A problem with such condition detection is that there may be an indeterminate time delay between the application/removal of voltage to the injector or solenoid and the switch activation (i.e., moving the valve needle out of or back into the valve seat) because the mechanical and/or hydraulic movement of the valve needle has some inertia. The switch is opened when voltage is still applied to the injector or solenoid valve, or, in the case of a long delay, only when voltage has been removed. A similar behavior occurs in the case of a switch closure. During the closing phase, voltage may or may not be applied to the injector or solenoid.

Despite the disadvantages listed above, measuring the current through the switch to detect the switch state, which in turn allows to conclude whether the injector is in the injection state or the off state. It must be taken into account that the switch cannot be loaded with a large current and that the current is limited to a few milliamperes with the aid of a resistor for efficiency reasons.

As long as the injector or solenoid is not activated, an output voltage (typically a vehicle battery voltage of 12 or 48 volts) must be applied through the pin of the injector or solenoid (coil) that is connected to the switch. Fig. 2 shows the case of detecting the current in the case just described by means of a measuring circuit (not shown). For example, it is assumed in fig. 2 that the current flowing through the resistor and the switch is 10 mA. The injector is therefore seen in a non-energized but closed position.

After the injector or solenoid has run simultaneously with the switch, several amperes of extra current must be fed to the injector or solenoid. This situation is illustrated in fig. 3. For example, assume that a typical value of current flowing through an injector or solenoid is 10A.

It is known from the prior art to perform current measurements on the input leads of the device. In this case, it is relatively easy to distinguish between a "de-energized (stromlos)" state and a "switch closed when the injector/solenoid is not energized" state. However, this is very challenging if a large current (e.g., 10A) flows through the injector or magnetic coil and only a few milliamps are added when the switch is closed. The detector must be very sensitive due to small variations in current.

The jump from 0mA to 10mA is easily detected. However, a change from 10A to 10.01A is difficult because the relative current increase is only 0.1%. If the resolution of the detection circuit is not high enough, there is a risk that this small increase will be considered as a disturbance or noise in the current. Thus, for a digital system with a resolution of 0.1%, the minimum requirement is at least a 10-bit system. In this case, a 0.1% variation implies a minimum uncertainty due to the system resolution. With such a high-resolution system, it is therefore not possible to make an exact distinction between actual changes in the values and disturbances or noise in the current intensity. Subsequent filters are also needed to improve detection reliability.

This means that current measurements have to be made using a particularly high-resolution system with signal filtering, which can lead to disturbing time delays due to the filtering, which is an undesirable side effect. It is therefore an object of the present invention to overcome the above-mentioned disadvantages of the prior art and to provide a device for condition detection of an injector which is superior to the known prior art.

Disclosure of Invention

This is achieved by a device according to claim 1, by which no signal filtering is required and no expensive high-resolution current measuring devices are required anymore. Further, the present invention can clearly detect the switching state even in a noisy environment that causes fluctuations in the current intensity. In addition, with the present invention, it is also possible to operate the ejector with only two cables leading from the housing in which the ejector is housed. Although a low resolution ammeter is used for condition detection, a third or even a fourth cable is not required.

The apparatus for condition detection of an injector according to the present invention includes: an injector for injecting fuel into a combustion chamber of an engine; a switch configured to change a switch state of the injector according to a state of the injector; and an evaluation unit for detecting a switching state of the switch, wherein a first switching contact of the switch is connected to the electrical input line of the injector and a second switching contact of the switch is connected to ground. The device according to the invention is further characterized in that the evaluation unit is configured with a first current measurer for the current flowing into the injector and the switch and a second current measurer for the current flowing into the injector.

A current meter is understood to mean any meter that is able to draw conclusions about the current flowing into the wire. In this case, it is not absolutely necessary to measure the current directly.

The present invention thus provides a solution to the following problems: how to use two cables for driving the injector and in this case the two cables can be used simultaneously for detecting the switch state without uncertainty due to signal noise and limited resolution. In contrast to the prior art, in which the current or voltage is measured absolutely and this measurement is compared with a predetermined level (10A or 10.01A), the present invention uses a difference measurement. In this case, the current flowing into the injector (or into the housing in which the injector is housed) and the current flowing out of the injector are measured. By means of an evaluation taking these two measured values into account, a state detection of the injector can be carried out, in which all disturbing factors of the superimposed currents are eliminated, so that the switching state can be detected particularly precisely.

This is preferably achieved if the evaluation unit is also designed to determine the switching state of the switch on the basis of the difference between the measured values of the first current measurer and the second current measurer. The difference between these two values will automatically cancel all superimposed signals. The result is only the current through the switch. This achieves the advantage over the asymmetry measurement used in the prior art that all disturbing signals and compensation currents are eliminated. The interference affects both current measurements to the same extent, so that the result is not affected by the subsequent formation of a difference. If the switch is closed, a small signal will be generated after the difference is made, but is easily detected.

In this case, the manner of detecting the switch state is inventive compared to the prior art. Instead of measuring the absolute voltage by pulling up or pulling down a resistor, or measuring the current absolutely and trying to determine the increase in the change of state of the switch, the current flowing to the injector and flowing back again from the injector is measured symmetrically. The difference between these two measurements is used as an indicator of a change in the state of the switch. In this case, it is advantageous if the symmetrical measurement eliminates superimposed interference currents and noise. In this case, the result obtained corresponds to the value of the current through the switch. In the ideal case, subsequent filtering of the result can be dispensed with.

According to an optional refinement of the invention, the injector is configured to be switched between an injection state and a closed state, wherein the switch further assumes a first switching state when the injector is in the injection state and a second switching state when the injector is closed. Thus, for example, provision may be made for the switch to be in the closed state when the injector is in the injection state (in which the nozzle needle is or has been turned into the extended state). On the other hand, if the nozzle needle returns to its initial reset position again (in which the injector is not given fuel), the switch goes to the off state.

The state of the switch is therefore dependent on the state of the injector.

Preferably, the first switching contact can be connected to the input line of the injector via a resistor.

This ensures that the current flowing when the switch is closed can be set to a lower value, so that the overall energy efficiency is not unduly reduced. In this case, it should be noted that the first current measurer is disposed in front of the connection point of the lead wire to the resistance. In this case, it must be ensured that the first current measurer measures not only the current flowing through the switch but also the current flowing through the injector.

It may further be provided that the second switching contact is connected to the same ground as the electric circuit of the injector, in which case it is preferably the body or the engine block of the vehicle. In this case, the second switching contact can also be connected to ground in the following manner: by being connected to the injector housing, the injector itself is grounded. Thus, an injector housing may be provided: with only two cables or contacts to the outside allowing particularly simple handling.

It can furthermore be provided that the evaluation unit further comprises a filter in order to filter the difference between the two measured values obtained by the first current measurer and the second current measurer.

This makes it easier to determine whether the switch is in a particular state.

According to an alternative refinement of the invention, the injector and the switch are arranged in a common housing, which comprises the input line, the output line and the ground line. Since the ground connection of the injector is usually also realized by means of the device used or the protective frame (Aufnahme) of the housing, the housing can therefore only have exactly two connections to the outside (e.g. lines, plug connections, etc.).

According to an advantageous embodiment of the invention, the first current measuring device of the evaluation unit is arranged on the input line of the housing and the second current measuring device of the evaluation unit is arranged on the output line of the housing.

This ensures that the measured current values can be used to obtain the achievable advantages of the invention.

In this case, the ground line of the housing is preferably connected to the second contact of the switch.

Furthermore, it can be provided that the injector is a solenoid valve injector, wherein the solenoid valve is preferably designed to cause a change in state of the injector, which in turn influences a change in state of the switch.

According to a preferred embodiment of the invention, the switch changes its state due to a movement of an injector component, preferably due to a movement of a valve needle of the injector.

Furthermore, according to a further development of the invention, it can be provided that the injector is a common rail injector.

The invention also relates to a method for detecting the state of an injector (2) according to the preamble of claim 1, wherein, in the method: the sum of the current flowing into the injector and the current flowing into the switch is measured by a first current measurer, the current flowing only through the injector is measured by a second current measurer, and the current actually flowing through the switch is inferred from the difference between the first current measurer and the second current measurer.

It may be further provided that the result of the difference between the first current measuring device and the second current measuring device is filtered.

The invention also relates to an internal combustion engine having a device according to one of the variants discussed above.

Drawings

Other advantages, features and details of the present invention will become apparent from the following description of the drawings. Shown in the attached drawings:

fig. 1 to 3: for the purpose of explaining the schematic diagram of the prior art,

FIG. 4: a schematic view of the apparatus according to the invention,

FIG. 5: a first embodiment of the invention is schematically illustrated, and

FIG. 6: schematic diagram of a second embodiment of the present invention.

Detailed Description

Fig. 1 to 3 have been explained in the background section of the description. Here, reference numeral 2 denotes an injector that closes or opens a switch 3 when its state changes. In this case, the first contact of the switch 3 is connected to one of the two lines leading from the injector 2 via a resistor 6. As a result, when the switch 3 is closed, current flows through the resistor 6, which in turn flows through the housing 8 of the device to ground 5.

Exemplary values of the flowing current are shown in fig. 2 and 3. Fig. 2 shows the injector 2 in a non-energized state, but with the switch 3 in a closed state. By means of a corresponding design of the resistor 6, a current of 10mA flows through the switch 3.

Fig. 3 shows a state in which the injector 2 is energized and the switch 3 is closed. It can be seen that in addition to 10mA flowing through resistor 6 and switch 3 connected to ground 5, 10A also flows through injector 2. If it is now desired to be informed of the switching state, it is generally necessary according to the prior art to determine the inflow current, which is the combination of the current flowing through the switch and the current flowing through the injector 2. Which leads to the disadvantages discussed in more detail in the background section of the specification.

Fig. 4 shows a schematic diagram of the present invention. The device 1 has an injector 2 adapted to release fuel in a dosed manner into the combustion chamber of the engine. For this reason, the injector 2 may be in a first state in which no fuel escapes and a second state in which fuel is injected. If the injector 2 is in the second state, in which fuel is being injected, the switch 3 is closed. Since the first contact 31 of the switch 3 is connected to the power supply line 21 of the injector 2 via the resistor 6, the current from the energy source of the device 1 flows through the switch 3 and flows in the direction of the ground 5. The second contact 32 of the switch 3 is connected to ground 5. In this case, the connection can be made via the housing 8 of the device 1 to the ground 5. Therefore, it is not necessary to provide another wire led out from the housing 8. This improves the operation of the device 1 and reduces the number of components which are prone to failure. In this case, the second contact 32 of the switch 3 is connected only to the housing 8 of the device 1.

Two

lines

81, 82 lead out of the housing 8, wherein the first line 81 has a branch to the resistor 6 between the housing 8 and the current input of the injector 2. A second line 82 which leads from the housing 8 connects the ground 5 to the current output of the injector 2.

Current measuring devices

41 and 42 are provided on the two

lead wires

81 and 82, respectively. The results of the two

current measurers

41, 42 are fed to a difference module 43, which outputs as a result the difference between the two measured values. This makes it possible to easily detect a relatively small current flowing through the switch 3 in the presence of noise or other current superposition.

Provision can also be made for the evaluation unit 4 to be integrated in the housing 8.

Fig. 5 shows a specific embodiment of the present invention. Here, the current is output from the control logic 9 in the direction of the injector (for simplicity, the injector is shown here as injector coil 23) and the resistor 6. Before the current is divided between ground 5 in the direction of the resistance and ground 5 in the direction of the injector coil 23, the current intensity is measured by a shunt resistance 411 and an operational amplifier 412. In this case, the first current measurer 41 measures the current I flowing through the resistance 6 _CT And a current I flowing through the injector _HS 。

In this case, the second current measurer 42 also measures by means of a shunt resistor 421, wherein the current flowing through the shunt resistor is determined by a further operational amplifier 422. The two

operational amplifiers

412 and 422 have the same amplification factor k. In addition, the two outputs of the operational amplifiers (OPVs) 412 and 422 are provided to the difference module 43. Thus, the voltage difference of the voltage drop across the two shunt resistors 411 and 421 can be determined and passed to the filter 7. Since the voltage drop across the shunt resistors 411 and 421 (amplified by the amplification factor k of the two OPVs 412 and 422) is substantially proportional to the current flowing through the shunt resistors, the current flowing into the

respective shunt resistors

412 and 422 can be measured.

Fig. 6 shows another embodiment of the invention with a transformer. As an alternative to the measurement with

operational amplifiers

412 and 422, a transformer 423 may also be used. This only works under alternating current and also enables the point in time at which the switch 3 is operated to be detected. In this case, the polarity of the pulse from the transformer 423 indicates the opening or closing of the switch 3.

The basic functional principle of the exemplary embodiment shown in fig. 6 is here the same as the solution described in more detail above, so that a detailed description may be omitted.

It is also clear to the person skilled in the art that a large number of different circuits may be used for detection, of which only a few are shown to be very specific.

If the injector is not energized, detection will not be possible. For example, if all current has been reduced, the injector is still in an open state due to inertia. In this case, the off time will not be available.

This can be solved by feeding a small current from the on-board system voltage via a resistor to the injector on the injector line connected to the resistor. In this case, a few milliamperes of current that permanently flows as "offset current" is also sufficient, so that detection can be carried out at any time even if the injector is not activated at all.

Claims

1. A device (1) for condition detection of an injector (2), comprising:

an injector (2) for injecting fuel into a combustion chamber of an engine,

a switch (3) configured to change a switching state of the injector according to a state of the injector (2), an

An evaluation unit (4) for detecting a switching state of the switch (3),

wherein the content of the first and second substances,

the first contact (31) of the switch (3) is connected to a supply line (21) of the injector (2), and

a second contact (32) of the switch (3) is connected to ground (5),

it is characterized in that the preparation method is characterized in that,

the evaluation unit (4) is designed to have a current (I) for the current flowing into the injector (2) and the switch (3) _HS ，I _CT ) And a first current measuring device (41) for the current (I) flowing into the injector (2) _LS ) Wherein the second current measurer (42) of (1),

the evaluation unit (4) is further configured to: the switching state of the switch (3) is determined on the basis of the difference between the measured value of the first current measurer (41) and the measured value of the second current measurer (42).

2. The device (1) according to claim 1,

the injector (2) is configured to be switched between an injection state and a closed state, and

the switch (3) assumes a first switch state when the injector (2) is in the injection state, and the switch (3) assumes a second switch state when the injector (2) is in the closed state.

3. Device (1) according to any one of the preceding claims, wherein the first contact (31) is connected to a power supply line (21) of the injector (2) via a resistor (6).

4. Device (1) according to any one of claims 1-2, wherein the second contact (32) is connected to the same ground (5) as the electrical circuit of the injector (2).

5. Device (1) according to claim 4, wherein the ground (5) is the bodywork of a vehicle or an engine block.

6. The device (1) according to any one of claims 1-2, wherein the evaluation unit (4) further comprises a filter (7) to filter the difference between the two measurements obtained by the first current measurer (41) and the second current measurer (42).

7. The device (1) according to any one of claims 1-2, wherein the injector (2) and the switch (3) are arranged in a housing (8) having an input lead (81), an output lead (82) and a ground lead (83).

8. The device (1) according to claim 7, wherein a first current measurer (41) of the evaluation unit (4) is arranged on the input lead (81) of the housing (8) and a second current measurer (42) of the evaluation unit (4) is arranged on the output lead (82).

9. Device (1) according to claim 7, wherein the ground line (83) is connected to the second contact (32) of the switch (3).

10. The device (1) according to any one of claims 1-2, wherein the injector (2) is a solenoid valve injector (2).

11. Device (1) according to claim 10, wherein the solenoid valve is configured to cause a change of state of the injector (2), which in turn causes a change of state of the switch (3).

12. Device (1) according to any one of claims 1-2, wherein the switch (3) changes its state due to the movement of an ejector component.

13. Device (1) according to claim 12, wherein the switch (3) changes its state due to a movement of a valve needle of the injector (2).

14. The device (1) according to any of claims 1-2, wherein the injector (2) is a common rail injector.

15. A method for an arrangement for condition detection of an injector (2) according to claim 1, wherein in the method:

measuring the current (I) flowing into the injector (2) by means of a first current measurer (41) _HS ) And a current (I) flowing into the switch (3) _CT ) The sum of the total weight of the components,

measuring only the current (I) flowing through the injector (2) by means of a second current measurer (42) _LS ) And are each and every

The difference between the first current measuring device (41) and the second current measuring device (42) represents the current (I) actually flowing through the switch (3) _CT )。

16. The method according to claim 15, wherein the result of the difference between the first current measurer (41) and the second current measurer (42) is subjected to a filter (7).

17. An internal combustion engine having a device (1) according to any one of the preceding claims 1 to 14.